The first tools for ultrasonic impact treatment based on magnetostrictive transducers were described in USSR Inventor's Certificate No. 472782 of Jul. 4, 1972. Practically, this tool has not been changed for more than 30 years. Today, the requirements for stability, technological effectiveness and reliability of ultrasonic tools have significantly increased due to, among other things, the appearance of new metals and alloys.
The basic hand tool for ultrasonic impact treatment has the following basic components: a magnetostrictive transducer with a concentrator of oscillating velocity, waveguides and indenters, which when combined comprise an oscillating system (OS); a transducer case with pumpable cooling liquid (water, cooling agent); lock nuts, a pin holder, a spring coupling and a body with a handle. Both magnetostrictive and piezoceramic ultrasonic transducers have been well-known for more than 50 years. For a number of years, the shape of both types of transducers has not been considerably changed. Conventionally, the transducer is a rod or rods made of piezo-active material with clamp plates reducing frequency, or resonance waveguides, such as transformers of oscillating velocity. Presently in the market of strengthening ultrasonic technologies, powerful tools have a short time to failure during treatment of such materials as cast iron, stainless steel, high-tensile steels and alloys of aluminum, titanium, copper, etc.
Magnetostrictive transducers are used under impulse impact load during ultrasonic impact treatment. During this process, the active components of the transducers are subjected to limiting mechanical stresses for the material from which they are made. The known manufacturing techniques of magnetostrictive transducers do not allow consistency of amplitude-frequency and energy characteristics of oscillating systems. The main oscillating system manufacturing steps are core manufacture and assemblage, concentrator manufacture, core annealing, brazing, and impregnation.
Today in the world, the manufacture of powerful specific-purpose magnetostrictive transducers is custom-made and small-scale. Transducer manufacturing technique results in scatter up to 30% of the parameters of oscillating systems based on those transducers. This makes it impossible to use such transducers under continuous manufacturing conditions where the main performance criterion for equipment is stability and repeatability of characteristics, oscillating system reliability and an agreement thereof with current standards and hence the interchangeability thereof.
Piezoceramic transducers have a wide distribution in treatment under constant load in such procedures as ultrasonic cleaning, impregnation, etc., which are carried out in liquid environments as a rule. Piezoceramics are known not to stand a great impact effect. Today, attempts are made to use piezoceramics for ultrasonic impact treatment at low power up to 500 Watts (W) with a static tool pressure up to 50 N, such as disclosed in U.S. Pat. No. 6,467,321. However, these tools can be used only for specified purposes for treating materials with low strength and consequently, the tools do not have an extensive use for work hardening. Oscillating systems based on piezoceramics cannot ensure sufficiently high power level and a resistance to impact and dynamic loads required for treatment of most known structural materials.